Challenges and considerations in liposomal hydrogels for the treatment of infection

INTRODUCTION

Liposomal hydrogels are novel drug delivery systems that comprise preformed liposomes incorporated in hydrogels destined for mostly localized drug therapy, herewith antimicrobial therapy. The formulation benefits from versatility of liposomes as lipid-based nanocarriers that enable delivery of various antimicrobials of different lipophilicities, and secondary vehicle, hydrogel, that assures better retention time of formulation at the infection site. Especially in an era of alarming antimicrobial resistance, efficient localized antimicrobial therapy that avoids systemic exposure of antimicrobial and related side effects is crucial.

AREAS COVERED

We provide an overview of liposomal hydrogels that were developed for superior delivery of antimicrobials at different infections sites, with focus on skin and vaginal infections. The review summarizes the challenges of infection site and most common infection-causing pathogens and offers commentary on most relevant features the formulation needs to optimize to increase the therapy outcome. We discuss the impact of liposomal composition, size, and choice of polymer-forming hydrogel on antimicrobial outcome based on the literature overview and own experience in the field.

EXPERT OPINION

Liposomal hydrogels offer improved therapy outcome in localized antimicrobial therapy. By fine-tuning of liposomal as well as hydrogel properties, formulations with superior performance can be optimized targeting specific infection site.

Utilization of propranolol hydrochloride mucoadhesive invasomes as a locally acting contraceptive: in-vitro, ex-vivo, and in-vivo evaluation

It was found that propranolol hydrochloride (PNL), which is a beta-blocker used for hypertension treatment, has a potent spermicidal activity through local anesthetic activity or beta-blocking effect on sperm cells subsequently it could be used as a contraceptive remedy. This study aimed to entrap PNL into invasomes (INVs) and then formulate it as a locally acting contraceptive gel. PNL-loaded mucoadhesive INVs were prepared via the thin-film hydration technique. The D-optimal design was utilized to fabricate INVs employing lipid concentration (X₁), terpenes concentration (X₂), terpenes type (X₃), and chitosan concentration (X₄) as independent variables, while their impact was observed for entrapment efficiency percent (Y₁; EE%), particle size (Y₂; PS), zeta potential (Y₃; ZP), and amount of drug released after 6 h (Y₄; Q6h). Design Expert® was bestowed to nominate the desired formula. The selected INV was subjected to further studies and formulated into a mucoadhesive gel for ex-vivo and in-vivo investigations. The optimum INV showed a spherical shape with EE% of 65.01 ± 1.24%, PS of 243.75 ± 8.13 nm, PDI of 0.203 ± 0.01, ZP of 49.80 ± 0.42 mV, and Q6h of 53.16 ± 0.73%. Differential scanning calorimetry study asserted the capability of INVs to entrap PNL. Permeation studies confirmed the desired sustained effect of PNL-loaded INVs-gel compared to PNL-gel, INVs, and PNL solution. Sperm motility assay proved the potency of INVs-gel to inhibit sperm motility. Besides, the histopathological investigation verified the tolerability of the prepared INVs-gel. Taken together, the gained data justified the efficacy of PNL-loaded INVs-gel as a potential locally acting contraceptive.

Nanomedicines for the topical treatment of vulvovaginal infections: Addressing the challenges of antimicrobial resistance

Recent years have, surprisingly, witnessed an increase in incidence of sexually transmitted infections (STIs). At the same time, antimicrobial therapy came under the threat of ever rising antimicrobial resistance (AMR), resulting in STIs with extremely limited therapy options. In this review, we addressed the challenges of treating vaginal infections in an era of AMR. We focused on published work regarding nanomedicine destined for localized treatment of vaginal infections. Localized therapy offers numerous advantages such as assuring high drug concentration at the infection site, limiting systemic drug exposure that can lead to faster development of AMR reduction in the systemic side effects and potentially safe therapy in pregnancy. We provided a state-of-the-art overview of nanoformulations proposed to topically treat STIs, emphasizing the challenges and advantages of each type of nanocarriers, as well as issues of potential toxicity.

Recent Advances in Nanosystems and Strategies for Vaginal Delivery of Antimicrobials

Vaginal infections such as bacterial vaginosis (BV), chlamydia, gonorrhea, genital herpes, candidiasis, and trichomoniasis affect millions of women each year. They are caused by an overgrowth of microorganisms, generally sexually transmitted, which in turn can be favored by alterations in the vaginal flora. Conventional treatments of these infections consist in systemic or local antimicrobial therapies. However, in the attempt to reduce adverse effects and to contrast microbial resistance and infection recurrences, many efforts have been devoted to the development of vaginal systems for the local delivery of antimicrobials. Several topical dosage forms such as aerosols, lotions, suppositories, tablets, gels, and creams have been proposed, although they are sometimes ineffective due to their poor penetration and rapid removal from the vaginal canal. For these reasons, the development of innovative drug delivery systems, able to remain in situ and release active agents for a prolonged period, is becoming more and more important. Among all, nanosystems such as liposomes, nanoparticles (NPs), and micelles with tunable surface properties, but also thermogelling nanocomposites, could be exploited to improve local drug delivery, biodistribution, retention, and uptake in vulvovaginal tissues. The aim of this review is to provide a survey of the variety of nanoplatforms developed for the vaginal delivery of antimicrobial agents. A concise summary of the most common vaginal infections and of the conventional therapies is also provided.

Nanomedicine in the development of anti-HIV microbicides

Prevention plays an invaluable role in the fight against HIV/AIDS. The use of microbicides is considered an interesting potential approach for topical pre-exposure prophylaxis of HIV sexual transmission. The prospects of having an effective product available are expected to be fulfilled in the near future as driven by recent and forthcoming results of clinical trials. Different dosage forms and delivery strategies have been proposed and tested for multiple microbicide drug candidates presently at different stages of the development pipeline. One particularly interesting approach comprises the application of nanomedicine principles to the development of novel anti-HIV microbicides, but its implications to efficacy and safety are not yet fully understood. Nanotechnology-based systems, either presenting inherent anti-HIV activity or acting as drug nanocarriers, may significantly influence features such as drug solubility, stability of active payloads, drug release, interactions between active moieties and virus/cells, intracellular drug delivery, drug targeting, safety, antiviral activity, mucoadhesive behavior, drug distribution and tissue penetration, and pharmacokinetics. The present manuscript provides a comprehensive and holistic overview of these topics as relevant to the development of vaginal and rectal microbicides. In particular, recent advances pertaining inherently active microbicide nanosystems and microbicide drug nanocarriers are discussed.

A review of the nonclinical safety of Transcutol®, a highly purified form of diethylene glycol monoethyl ether (DEGEE) used as a pharmaceutical excipient

Transcutol® (Diethylene glycol monoethyl ether, DEGEE), CAS # 111-90-0, is commonly used as a vehicle in the formulation or manufacturing process of pharmaceuticals, cosmetics, and food additives. This paper presents unpublished nonclinical safety data using a form of DEGEE which includes a significantly decreased level of impurities, specifically ethylene glycol and diethylene glycol. It also reviews the history of use, regulatory status, and previously published toxicity data for DEGEE. The review supports that DEGEE is well tolerated across animal species and gender with toxicity occurring only at levels well above those intended for human use. At high levels of exposure, the kidney is identified as the critical target organ of DEGEE toxicity. DEGEE is negative for genotoxicity in in vitro and in vivo studies. Subchronic and chronic toxicity studies produced no reports of preneoplastic changes in organs, but the animal data is insufficient to allow a definitive opinion as to carcinogenicity. In silico data suggested that DEGEE is not carcinogenic or genotoxic. Developmental toxicity was seen in rats but only at levels 200 times greater than the estimated oral Permissible Daily Exposure Level of 10 mg/kg/day. The nonclinical data along with the long history of DEGEE use as a vehicle and solvent by multiple routes provide evidence of its safety. Furthermore, the novel data discussed herein provides evidence that toxicity previously associated with high levels of DEGEE in nonclinical studies conducted prior to 1990 could possibly be attributed to the presence of significant amounts of ethylene glycol or other impurities.